Perpendicular magnetic recording medium and magnetic recording apparatus

ABSTRACT

To provide an improved perpendicular magnetic recording medium suitable for high density magnetic recording. In a perpendicular magnetic recording medium comprising a perpendicular magnetic layer and protective layer provided on a non-magnetic substrate via a soft magnetic backlayer, a polycrystalline MgO film is inserted between the soft magnetic backlayer and perpendicular magnetic layer.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a magnetic recording medium comprising amagnetic layer suitable for high density magnetic recording, and to amagnetic recording apparatus using this medium.

2. Description of the Related Art

Magnetic disk apparatuses currently in use employ the in-plane magneticrecording method. In this method, there is a technical problem informing an in-plane magnetic domain parallel to a substrate on anin-plane magnetic recording medium which is easily magnetized in adirection parallel to the disk substrate surface. In in-plane recording,as the magnetizations are adjacent to each other in mutually oppositedirections, the thickness of the recording layer must decrease as thecoercivity of the layer is increased so as to extend the linearrecording density. Due to thermal fluctuations when the thickness of therecording layer decreases, the intensity of recorded magnetizationdecreases and in extreme cases, the recorded information may be lost.Also, in the in-plane recording method, if Co alloy is used for therecording layer as in the prior art, it is difficult to achieve an arealrecording density of not less than 20 Gb/in².

In the perpendicular magnetic recording method, magnetizations areperpendicular to the surface of a film medium, so the magnetic recordingprinciple and the mechanism whereby noise arises from the medium differsfrom the case of prior art in-plane magnetic recording media. Due to thefact that magnetizations are in complementary directions, this method issuitable for high density magnetic recording. It is therefore becomingmore common and various structures have been proposed for media suitablefor perpendicular magnetic recording. A method is presently been studiedwhere a non-magnetic base material is provided between a perpendicularmagnetized layer of Co alloy and a substrate to improve theperpendicular orientation characteristics of the perpendicularmagnetized layer. For example, in JP-A No. S58-77025 and No. S58-141435,a method is disclosed for forming a Ti film as the base layer of a Co—Crmagnetic layer, in JP-A No. S60-214417, a method is disclosed using Geor Si as the base layer, and in JP-A No. S60-064413, oxide base layermaterials such as CoO and NiO are used.

These single-layered perpendicular magnetic recording media comprising asingle perpendicular magnetic layer employ a thin film ring head forrecording.

To improve the recording efficiency of perpendicular magnetic recording,it is effective to combine a single pole type of recording head with aperpendicular magnetic recording medium having two magnetic layers. Amedium wherein a soft magnetic layer of permalloy or Co alloy isprovided between the substrate and the perpendicular magnetic layer hasbeen studied as an example of a bi-layered perpendicular magneticrecording medium. However, in bi-layered perpendicular magneticrecording media, the intensity of perpendicular magnetic anisotropy ofthe recording magnetic layer was inadequate compared to single-layeredperpendicular magnetic recording media.

If a perpendicular magnetic recording medium is to achieve high densityrecording of 20 Gb/in² or more, the linear recording density resolutionmust be high, the noise due to the medium must be low, and recordingmust be performed efficiently by a thin film head. For this purpose, theperpendicular magnetic layer must have a fine magnetic crystal grain,the perpendicular magnetic anisotropy must be increased, and therecording magnetic field of the magnetic head must effectively penetrateinside the medium.

BRIEF SUMMARY OF THE INVENTION

It is therefore an object of this invention to provide a perpendicularmagnetic recording medium which has high resolution so as to achieve ahigh recording density of 30 Gb/in², has low noise characteristics, andpermits a high density magnetic recording apparatus to be easilyconstructed.

Perpendicular magnetic recording media which offer high recordingefficiency by a magnetic head are bi-layered perpendicular magneticrecording media. According to this invention, to achieve the aforesaidobject, a super-thin MgO film is introduced between a soft magneticbacklayer formed on a substrate and a Co alloy perpendicular magneticlayer having a hexagonal close-packed structure. To ensure that theobject of this invention is achieved, a super-thin non-magnetic film ofa special material is formed in the lower part and/or upper part of theMgO film.

The soft magnetic backlayer used in the bi-layered perpendicularmagnetic recording medium is generally a polycrystalline film having apermalloy of Ni or the like as its main component, a polycrystallinefilm like Sendust having Fe as its main component, or a Co alloy such asCo—Nb—Zr. When the perpendicular magnetic layer of Co alloy is formeddirectly on this soft magnetic backlayer, in the initial growth state ofthe thin film, it contains an initial growth layer which is undesirablefor a perpendicular magnetic layer wherein the crystal growth is random.As a result, there is a decrease of perpendicular magnetic anisotropy,and the magnetic separation between the magnetic crystal grains formingthe perpendicular magnetic layer is insufficient, which leads to adecrease of coercivity or increase of noise.

The inventors found that the introduction of the super-thin film of MgObetween the soft magnetic back layer and the perpendicular magneticlayer comprising Co alloy was effective in dealing with this problem.When the MgO film is formed on the soft magnetic backlayer having anamorphous structure, MgO microcrystalline grains are formed wherein the(100) plane is substantially parallel to the substrate, and as a result,a polycrystalline MgO oriented film grows wherein the (100) plane isessentially disposed parallel to the substrate. The (100) plane of MgOis energetically most stable crystallographic plane, and thus the (100)oriented MgO crystal grains tend to be formed when deposited on a flatsurface. When a substrate has surface undulations, the (100) MgO planehas a slight misorientation, but substantially the (100) plane is almostparallel to the substrate surface. When the perpendicular magnetic layerof Co alloy is formed on this oriented film, magnetic crystal grainsgrow having a hexagonal close-packed structure with an easilymagnetization [0001] axis perpendicular to the substrate, andperpendicular magnetic anisotropy therefore increases.

The thickness of the MgO film required to produce this effect is 1 nm orgreater. If the thickness of the MgO film is made too large, thedistance between the soft magnetic backlayer and perpendicular magneticlayer increases, so recording efficiency when recording is performed bya magnetic head decreases. The linear recording density required toachieve an areal recording density of 30 Gb/in² or more is at least 300kFCI, and to increase the efficiency of the recording head at this highlinear recording density, the gap between the two magnetic films mustnot exceed 20 nm.

Also, the crystal grains of the MgO film become larger the more the filmthickness increases. The magnetic crystal grains which grow on thesecrystal grains are affected by the MgO crystal grain diameter. Hence thediameter of the crystal grains forming the magnetic film, which is themedium on which magnetic recording is performed at high density, mustnot exceed 20 nm but preferably does not exceed 15 nm, and it ispreferable that the thickness of the MgO film is less than 13 nm.

When the soft magnetic backlayer has a polycrystalline structure, andeven when it has an amorphous structure, it is effective to introduce asuper-thin non-magnetic layer between the soft magnetic backlayer andMgO film to improve the (100) orientation characteristics of the MgOpolycrystalline film. For this purpose a non-magnetic layer having anamorphous structure is particularly desirable. Materials which exhibitthis desirable effect in the region when the film thickness does notexceed 10 nm are Ti, Zr, Hf, Cr, Mo, Nb, V, W, Si, Ge, B, C or alloyshaving these elements as their main component, or oxides chosen from thegroup SiO₂, Al₂O₃ and ZrO₂. If the MgO film is formed via the film ofthis non-magnetic material, its (100) orientation characteristics arelargely improved.

The perpendicular magnetic layer of Co alloy may be formed on the (100)oriented MgO polycrystalline film, but to further promote noisereduction of the magnetic recording medium, it is effective to provide asuper-thin non-magnetic layer having a hexagonal close-packed structureof several nm or less on the MgO film. By interposing this non-magneticlayer, the magnetic separation between magnetic crystals of the Co alloyperpendicular magnetic layer is particularly enhanced in the initialgrowth region. As both of these have the same hexagonal close-packedstructure, epitaxial growth occurs wherein the crystal lattice growscontinuously. This epitaxial growth is also effective in reducingcrystal defects in the magnetic film and in achieving a desirablecoercivity.

Examples of materials having a hexagonal close-packed structure withthis effect are Co—Cr, Co—Cr—X (X=Mn, V, Zr, Hf, Nb, Mo, W, Si, B, Ta,Cu) where the addition amount of the non-magnetic element to Co exceeds30 at %, or Ru, Ru—Y alloy (Y=Mn, Cr, Al, Cu), Ti, or Ti—Z alloy (Z=Co,Ni, Mn, Cu, Al).

In any case, for the magnetic recording medium to permit a recordingdensity of 30 Gb/in², the distance between the soft magnetic backlayerand the perpendicular magnetic layer comprising Co must not exceed 20nm. The thickness of the MgO film in this case is in the range 1 nm to15 nm, but more preferably less than 13 nm. Further, the perpendicularmagnetic layer comprising Co is formed on the (100) orientedpolycrystalline MgO film directly or via a non-magnetic layer having ahexagonal close packed structure, but perpendicular magnetic layershaving other crystalline structures may also be formed on theperpendicular magnetic layer if necessary.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is a cross-sectional schematic view of one example of aperpendicular magnetic recording medium according to this invention.

FIG. 2 is a cross-sectional schematic view of another example of aperpendicular magnetic recording medium according to this invention.

FIG. 3 is a cross-sectional schematic view of another example of aperpendicular magnetic recording medium according to this invention.

FIGS. 4(a) and 4(b) are outline views of the construction of a magneticstorage apparatus.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Some embodiments of this invention will now be described referring tothe appended drawings.

[Embodiment 1]

A perpendicular magnetic recording medium having the cross-sectionalstructure shown in FIG. 1 was fabricated by magnetron sputtering using aglass substrate of diameter 2.5 inch. After forming a layer 12 forstrengthening the adhesion force on a substrate 11, a soft magneticbacklayer 13, MgO film 14, perpendicular magnetic layer 15 andprotective layer 16 were formed. A Cr target was used for the layer 12for strengthening adhesion force, a Co-8 at %Nb-4 at %Ta target was usedfor the soft layer 13, a MgO target was used for the MgO film 14, aCo-20 at %Cr-10 at %Pt-1.5 at %Ta target was used for the perpendicularmagnetic layer 15, and a carbon target was used for the protectivelayer. The Cr film of 20 nm-thickness, the Co—Nb—Ta film of 200nm-thickness, the MgO film of 10 nm-thickness, the Co—Cr—Pt—Taperpendicular magnetic layer of 25 nm-thickness, and the carbon layer of5 nm-thickness were formed respectively. An Ar gas pressure of 3 mTorrfor sputtering, sputter power of 10 W/cm², and substrate temperature of280° C. were used.

When the structure of this perpendicular magnetic recording medium wasexamined by a transmission electron microscope and X-ray diffraction, itwas found that the MgO film was a (100) oriented film with an averagecrystal grain diameter of 8 nm, and the Co—Cr—Pt—Ta perpendicularmagnetic layer grew epitaxially on the MgO crystal grains with the[0001] orientation as the preferred growth orientation.

As a comparison sample 1, the perpendicular magnetic recording mediumwas fabricated without an MgO film, and as a comparison sample 2, asingle layer magnetic recording medium was fabricated without the softmagnetic backlayer. A single pole type thin film head was used forrecording on the bi-layered perpendicular magnetic recording medium, anda head having a gap length of 0.2 μm was used for recording on thesingle-layered perpendicular magnetic recording medium. A giantmagneto-resistance (GMR) head having a head shield gap of 0.15 μm wasused for reproduction, the spacing between the head and medium surfaceduring measurements being 0.015 μm. To evaluate the characteristics, therecording resolution, reproduction output at low recording density, S/Nof the medium and the magneto-motive force of the writing head requiredfor saturation recording were measured. Recording resolution wasmeasured by the output half recording density (D₅₀) which is half thelow frequency reproduction output, reproduction output was measured bythe value of the reproduction output relative to comparison sample 2when recording was performed at 10 kFCI, and the S/N of the medium wasmeasured by the value of S/N relative to comparison sample 2 whenmagnetic recording was performed at 300 kFCI. These results are shown inTable 1.

TABLE 1 Magneto- motive force S/N of of writing Reproduction medium headResolution output (relative (relative Sample D₅₀ (kFC1) (relative value)value) value) This 268 2.3 1.4 0.21 invention Comparison 230 1.7 0.80.34 sample 1 Comparison 255 1.0 1.0 1.0 sample 2 (Comparison(Comparison (Comparison value) value) value)

The magnetic recording medium in this embodiment has a greatly improvedrecording resolution and medium S/N compared to comparison sample 1, andthe low density reproduction output and writing head magneto-motiveforce are also largely improved compared to comparison sample 2.

A 2.5 inch magnetic recording apparatus was manufactured using themagnetic recording medium fabricated in this embodiment, and using a GMRhead of track width 0.32 μm for recording with a single pole type thinfilm head of track width 0.4 μm as reproducing element. An error rate of10⁻⁹ was obtained at an areal recording density of 30 Gb/in², and it wasconfirmed that the apparatus functions as a super high-density magneticrecording apparatus.

[Embodiment 2]

A perpendicular magnetic recording medium having the cross-sectionalstructure shown in FIG. 2 was fabricated by magnetron sputtering using aglass substrate of diameter 2.5 inch. After forming a layer 22 forstrengthening the adhesion force on a substrate 21, a soft magneticbacklayer 23, seed layer 24, MgO film 25, perpendicular magnetic layer26 and protective layer 27 were formed. A Zr target was used for thelayer 22 for strengthening adhesion force, a Fe-8 at %Si-3 at %Al targetwas used for the soft layer 23, a Hf target was used for the seed layer24, a MgO target was used for the MgO film 25, a Co-21 at %Cr-8 at %Pt-2at %Nb target was used for the perpendicular magnetic layer 26, and acarbon target was used for the protective layer 27. The Zr film of 20nm-thickness, the Fe—Si—Al film of 400 nm-thickness, the Hf film of 3nm-thickness, the MgO film of 12 nm-thickness, the Co—Cr—Pt—Nbperpendicular magnetic layer of 25 nm-thickness, and the carbon layer of5 nm-thickness were formed respectively. An Ar gas pressure of 3 mTorrfor sputtering, sputter power of 10 W/cm², and substrate temperature of300° C. were used.

When the structure of this perpendicular magnetic recording medium wasexamined by a transmission electron microscope and X-ray diffraction, itwas found that the MgO film was a (100) oriented film with an averagecrystal grain diameter of 10 nm, and the Co—Cr—Pt—Nb perpendicularmagnetic layer grew epitaxially on the MgO crystal grains with the[0001] orientation as the preferred growth orientation. Next,perpendicular magnetic recording media of identical structure werefabricated excepting that a Ti, Zr, Cr, Mo, Nb, V, W, Si, Ge, B, C,SiO₂, Al₂O₃ or ZrO₂ target was used to form the seed layer.

As a comparison sample, the perpendicular magnetic recording medium wasfabricated under identical conditions without the MgO film. Therecording and reproduction characteristics of these perpendicularmagnetic recording media were measured under the following conditions. Asingle pole type thin film head was used for recording, and a greatmagnetic resistance (GMR) head having a head shield gap of 0.15 μm wasused for reproduction, the spacing between the head and medium surfaceduring measurements being 0.015 μm. To evaluate the characteristics, therecording resolution, reproduction output at low recording density andS/N of the medium were measured. Recording resolution was measured bythe output half recording density (D₅₀) which is half the low frequencyreproduction output, reproduction output was measured by the value ofthe reproduction output relative to the comparison sample when recordingwas performed at 10 kFCI, and the S/N of the medium was measured by thevalue of S/N relative to the comparison sample when magnetic recordingwas performed at 300 kFCI. These results are shown in Table 2.

TABLE 2 Reproduction Resolution output S/N of medium Sample No. Seedlayer (D₅₀k:FC1) (relative value) (relative value) 1 Hf 265 1.6 1.3 2 Ti255 1.5 1.5 3 Zr 275 1.4 1.4 4 Cr 251 1.8 1.3 5 Mo 245 1.5 1.4 6 Nb 2511.6 1.6 7 V 261 1.5 1.4 8 W 244 1.9 1.3 9 Si 269 1.7 1.7 10 Ge 265 1.71.7 11 B 261 1.9 1.9 12 C 238 1.2 1.2 13 SiO2 252 1.6 1.6 14 Al2O3 2501.5 1.5 15 ZrO2 265 1.5 1.5 Comparison Hf 210 1.0 1.0 Sample (Comparison(Comparison reference) reference)

The magnetic recording medium in this embodiment shows greatly improvedrecording resolution and medium S/N compared to the comparison sample.

[Embodiment 3]

A perpendicular magnetic recording medium having the cross-sectionalstructure shown in FIG. 3 was fabricated by magnetron sputtering using aglass substrate of diameter 2.5 inch. After forming a layer 32 forstrengthening the adhesion force on a substrate 31, a hard magneticlayer 33 and soft magnetic layer 34 as soft magnetic backlayer, seedlayer 35, MgO film 36, non-magnetic film 37 of a material having ahexagonal close-packed structure, perpendicular magnetic layer 38 andprotective layer 39 were formed. A Cr-10 at %Zr target was used for thelayer 32 for strengthening adhesion force, a Fe-35 at %Pt target wasused for the hard layer 33, a Ni-16 at %Fe-3 at %Mo target was used forthe soft layer 34, a Ge-35 at %Si target was used for the seed layer 35,a MgO target was used for the MgO film 36, a Co-28 at %Cr-8 at %Mntarget was used for the non-magnetic film 37 of material having ahexagonal close-packed structure, a Co-21 at %Cr-8 at %Pt-2 at %Nbtarget was used for the perpendicular magnetic layer 38, and a carbontarget was used for the protective layer. The Cr—Zr film of 20nm-thickness, the Fe—Pt film of 10 nm-thickness, the Ni—Fe—Mo film of150 nm-thickness, the Ge—Si film of 5 nm-thickness, the MgO film of 8nm-thickness, the Co—Cr—Mn film of 6 nm-thickness, the Co—Cr—Pt—Nbperpendicular magnetic layer of 25 nm-thickness, and the carbon layer of5 nm-thickness were formed respectively. An Ar gas pressure of 3 mTorrfor sputtering, sputter power of 10 W/cm², and substrate temperature of300° C. were used.

When the structure of this perpendicular magnetic recording medium wasexamined by a transmission electron microscope and X-ray diffraction, itwas found that the MgO film was a (100) oriented film with an averagecrystal grain diameter of 8.7 nm, and the Co—Cr—Pt—Nb perpendicularmagnetic layer grew epitaxially on the MgO crystal grains via thenon-magnetic film 37 of material having a hexagonal close-packedstructure, with the [0001] orientation as the preferred growthorientation.

Next, perpendicular magnetic recording media of identical structure werefabricated excepting that a Co-33 at %Cr, Co-30 at %Cr-5 at %Mn, Co-30at %Cr-4 at %V, Co-30 at %Cr-6 at %Zr, Co-30 at %Cr-4 at %Hf, Co-30 at%Cr-5 at %Nb, Co-30 at %Cr-2 at %Mo, Co-30 at %Cr-2 at %W, Co-30 at%Cr-2 at %Si, Co-30 at %Cr-3 at %B, Co-30 at %Cr-4 at %Ta, Co-30 at%Cr-6 at %Cu, Ru, Ru-10 at %Mn, Ru-4 at %Cr, Ru-3 at %Al, Ru-5 at %Cu,Ti or Ti-6 at %Mn target was used for the non-magnetic film of materialhaving a hexagonal close-packed structure. As a comparison sample, aperpendicular magnetic recording medium, comprising the perpendicularmagnetic layer 38 formed directly on the soft magnetic backlayer 34without the seed layer 35, the MgO film 36, and the non-magnetic layer37 of material having a hexagonal close-packed structure, was fabricatedunder identical conditions. The recording and reproductioncharacteristics of these perpendicular magnetic recording media weremeasured under the following conditions. A single pole type thin filmhead was used for recording, and a giant magneto-resistance (GMR) headhaving a head shield gap of 0.12 μm was used for reproduction, thespacing between the head and medium surface during measurements being0.014 μm. To evaluate the characteristics, the recording resolution,reproduction output at low recording density and S/N of the medium weremeasured. Recording resolution was measured by the output half recordingdensity (D₅₀) which is half the low frequency reproduction output,reproduction output was measured by the value of the reproduction outputrelative to the comparison sample when recording was performed at 10kFCI, and the S/N of the medium was measured by the value of S/Nrelative to the comparison sample when magnetic recording was performedat 300 kFCI. These results are shown in Table 3.

TABLE 3 Material having a hexagonal Resolution Reproduction output S/Nof medium Sample No. close-packed structure (D₅₀:kFC1) (relative value)(relative value) 1 Co-28 at % Cr-8 at % Mn 261 1.6 1.9 2 Co-33 at % Cr253 1.5 1.5 3 Co-30 at % Cr-5 at % Mn 247 1.4 1.9 4 Co-30 at % Cr-4 at %V 245 1.5 1.6 5 Co-30 at % Cr-6 at % Zr 245 1.5 1.4 6 Co-30 at % Cr-4 at% Hf 253 1.6 1.6 7 Co-30 at % Cr-5 at % Nb 241 1.5 1.7 8 Co-30 at % Cr-2at % Mo 241 1.4 1.5 9 Co-30 at % Cr-2 at % W 260 1.3 1.6 10 Co-30 at %Cr-2 at % Si 255 1.3 1.8 11 Co-30 at % Cr-3 at % B 260 1.4 1.9 12 Co-30at % Cr-4 at % Ta 248 1.2 1.7 13 Co-30 at % Cr-6 at % Cu 258 1.3 1.6 14Ru 250 1.3 1.2 15 Ru-10 at % Mn 245 1.3 1.6 16 Ru-4 at % Cr 228 1.2 1.517 Ru-3 at % Al 235 1.2 1.6 18 Ru-5 at % Cu 249 1.3 1.5 19 Ti 240 1.11.3 20 Ti-6 at % Mn 238 1.4 1.6 Comparison None 210 1.0 1.0 Sample(Comparison reference) (Comparison reference)

The magnetic recording medium in this embodiment shows greatly improvedrecording resolution and medium S/N compared to the comparison sample.

A magnetic storage device shown in FIG. 4 was fabricated using arecording/reproduction head having a high sensitivity reproductionelement using the tunnel magneto-resistance (TMR) effect and aperpendicular magnetic recording medium of which a prototype wasproduced in Embodiment 3. This magnetic storage device is a devicehaving a construction known in the art comprising a magnetic recordingmedium 41 rotation driven by a magnetic recording medium drive unit 42,a magnetic head 43 which performs recording and reproduction on themagnetic recording medium 41 when driven by a magnetic head drive unit44, and a signal processor 45 which processes the recording signal andreproduction signal from the magnetic head 43, as shown by the schematicplan view in FIG. 4(a) and a section taken through a line AA′ in FIG.4(b).

The track width of the recording head was 0.3 μm, the track width of theTMR head element for reproduction was 0.26 μm and the spacing betweenthe head and the medium was 15 nm. The EEPR4 system was used for signalprocessing, and when the apparatus was operated using a surfacerecording density of 55 Gb/in², an error rate of 10⁻⁸ or less wasobtained.

According to this invention, the resolution of the perpendicularmagnetic recording medium can be improved, noise can be reduced and ahigh S/N ratio is obtained, so a high density magnetic disk apparatuscan be fabricated. In particular, high density magnetic recording of 30Gb/in² can be performed, so the apparatus can be made compact and highcapacity.

DESCRIPTION OF REFERENCE NUMERALS

11 substrate, 12 layer for strengthening adhesion force, 13 softmagnetic layer, 14 MgO film, 15 perpendicular magnetic layer, 16protective layer, 21 substrate, 22 layer for strengthening adhesionforce, 23 soft magnetic layer, 24 seed film, 25 MgO film, 26perpendicular magnetic layer, 27 protective layer, 31 substrate, 32layer for strengthening adhesion force, 33 hard magnetic layer, 34 softmagnetic layer, 35 seed film, 36 MgO film, 37 film of material having ahexagonal close-packed structure, 38 perpendicular magnetic layer, 39protective layer, 41 magnetic recording medium, 42 magnetic recordingmedium drive unit, 43 magnetic head, 44 magnetic head drive unit, 45signal processor.

What is claimed is:
 1. A perpendicular magnetic recording medium whereina perpendicular magnetic layer is provided on a non-magnetic substratevia a soft magnetic backlayer, wherein a polycrystalline MgO film isinserted between said soft magnetic backlayer and said perpendicularmagnetic layer, and the perpendicular magnetic layer formed on saidpolycrystalline MgO film has a hexagonal close-packed structure, whereina distance between a surface of said soft magnetic backlayer and saidperpendicular magnetic layer is within 20 nm.
 2. A perpendicularmagnetic recording medium wherein a perpendicular magnetic layer isprovided on a non-magnetic substrate via a soft magnetic backlayer,wherein a polycrystalline MgO film is provided on said soft magneticbacklayer, a non-magnetic layer having a hexagonal close-packedstructure is provided on said polycrystalline MgO film, theperpendicular magnetic layer is provided on said non-magnetic layer, andsaid perpendicular magnetic layer has a hexagonal close-packedstructure, wherein a distance between a surface of said soft magneticbacklayer and said perpendicular magnetic layer is within 20 nm.
 3. Aperpendicular magnetic recording medium according to claim 1, wherein anon-magnetic layer comprising a material comprising Ti, Zr, Hf, Cr, Mo,Nb, V, W, Si, Ge, B, C or alloys having these elements as their maincomponent, or oxides selected from the group consisting of SiO₂, Al₂O₃or ZrO₂, is provided between said soft magnetic backlayer and saidpolycrystalline MgO film.
 4. A perpendicular magnetic recording mediumaccording to claim 2, wherein a non-magnetic layer comprising a materialcomprising Ti, Zr, Hf, Cr, Mo, Nb, V, W, Si, Ge, B, C or alloys havingthese elements as their main component, or oxides selected from thegroup consisting of SiO₂, Al₂O₃ or ZrO₂, is provided between said softmagnetic backlayer and said polycrystalline MgO film.
 5. A perpendicularmagnetic recording medium according to claim 2, wherein the thickness ofsaid polycrystalline MgO film is from 1 nm to less than 13 nm.
 6. Aperpendicular magnetic recording medium according to claim 3, whereinthe total film thickness of the non-magnetic layer formed between saidsoft magnetic backlayer and said perpendicular magnetic layer is from 2nm to less than 20 nm, and the thickness of said polycrystalline MgOfilm is from 1 nm to less than 13 nm.
 7. A magnetic recording apparatuscomprising a magnetic recording medium, a magnetic recording mediumdrive unit which drives said magnetic recording medium, a magnetic headwhich performs recording and reproduction on said magnetic recordingmedium, a magnetic head drive unit which drives said magnetic head, anda recording/reproduction signal processing system which processesrecording signals and reproduction signals sent to and from saidmagnetic head, wherein said magnetic recording medium comprises a softmagnetic backlayer provided on a non-magnetic substrate, apolycrystalline MgO film formed on said soft magnetic backlayer, and aperpendicular magnetic layer having a hexagonal close-packed structureprovided on said polycrystalline MgO film, said magnetic head isprovided with a thin film recording head part and a reproduction elementusing the giant magneto-resistance effect or magnetic tunnel effect, andsaid apparatus performs magnetic recording and reproduction at an arealrecording density of at least 30 Gb/in².
 8. A magnetic recordingapparatus comprising a magnetic recording medium, a magnetic recordingmedium drive unit which drives said magnetic recording medium, amagnetic head which performs recording and reproduction on said magneticrecording medium, a magnetic head drive unit which drives said magnetichead, and a recording/reproduction signal processing system whichprocesses recording signals and reproduction signals sent to and fromsaid magnetic head, wherein said magnetic recording medium comprises asoft magnetic backlayer provided on a non-magnetic substrate, apolycrystalline MgO film provided on said soft magnetic backlayer, anon-magnetic layer having a hexagonal close-packed structure provided onsaid polycrystalline MgO film and a perpendicular magnetic layer havinga hexagonal close-packed structure provided on said non-magnetic layer,said magnetic head is provided with a thin film recording head part anda reproduction element using the giant magnetic resistance effect ormagnetic tunnel effect, and said apparatus performs magnetic recordingand reproduction at an areal recording density of at least 30 Gb/in². 9.A magnetic recording apparatus comprising a magnetic recording medium, amagnetic recording medium drive unit which drives said magneticrecording medium, a magnetic head which performs recording andreproduction on said magnetic recording medium, a magnetic head driveunit which drives said magnetic head, and a recording/reproductionsignal processing system which processes recording signals andreproduction signals sent to and from said magnetic head, wherein saidmagnetic recording medium comprises a soft magnetic backlayer providedon a non-magnetic substrate, an non-magnetic layer comprising a materialcomprising Ti, Zr, Hf, Cr, Mo, Nb, V, W, Si, Ge, B, C or alloys havingthese elements as their main component, or oxides selected from thegroup consisting of SiO₂, Al₂O₃ or ZrO₂, provided on said soft magneticbacklayer, a polycrystalline MgO film provided on said non-magneticlayer, a non-magnetic layer having a hexagonal close-packed structureprovided on said polycrystalline MgO film and a perpendicular magneticlayer having a hexagonal close-packed structure provided on saidnon-magnetic layer, said magnetic head is provided with a thin filmrecording head part and a reproduction element using the giant magneticresistance effect or magnetic tunnel effect, and said apparatus performsmagnetic recording and reproduction at an areal recording density of atleast 30 Gb/in².